State Comptroller Thomas DiNapoli has zeroed in on scores of big-spending correction employees in a sweeping investigation to determine the extent of travel fraud at the Department of Correctional Services, The Post has learned.

The probe follows revelations Tuesday that the prison system’s former food boss, Howard Dean — with knowledge and approval of some superiors — bilked taxpayers out of nearly $500,000 by filing reams of improper travel expenses and playing hooky every Friday for 17 years.

Sources said probers are interested in whether the agency allowed other employees to pad their expenses with similar tricks, such as assigning workers to fictitious work stations so they can qualify for per diems.

A source with knowledge of the investigation said auditors were targeting employees with the biggest travel bills.

The comptroller’s office is “looking at the largest travel receipt recipients, and they’re checking to see if those are legitimate expenses,” the source said.

DiNapoli spokeswoman Jennifer Freeman confirmed the travel probe, but refused to discuss details beyond those contained in the report on Dean released Tuesday.

“There was an indication that this was accepted behavior, and there are concerns of widespread abuse, particularly at DOCS,” Freeman said.

Prison workers billed the state for $4 million in travel expenses in the fiscal year that ended March 31, down from $5.5 million in the prior year.